The block is handling its own caching in its hook_block_view(). From the
perspective of the block cache system, this is equivalent to DRUPAL_NO_CACHE.
Useful when time based expiration is needed or a site uses a node access
which invalidates standard…

The block or element can change depending on the user viewing the page.
This setting can be resource-consuming for sites with large number of users,
and thus should only be used when DRUPAL_CACHE_PER_ROLE is not sufficient.

The standard log2 number of iterations for password stretching. This should
increase by 1 every Drupal version in order to counteract increases in the
speed and power of computers available to crack the hashes.